Method and apparatus for providing acknowledgement bundling

ABSTRACT

An approach is provided for acknowledgement bundling. Dynamically scheduling of one or more of subframes per bundling window is performed by reusing an assignment index field (e.g., downlink assignment index (DAI) field). The assignment index field has a value greater than or equal to number of previously assigned subframes within the bundling window. The bundling window defines a group of subframes for common acknowledgement.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/489,988, filed Jun. 23, 2009, which claims the benefit of the earlierfiling date under 35 U.S.C. §119(e) of U.S. Provisional Application Ser.No. 61/074,923 filed Jun. 23, 2008, entitled “Method and Apparatus forProviding Acknowledgement Bundling,” the entireties of which areincorporated herein by reference.

BACKGROUND

Radio communication systems, such as a wireless data networks (e.g.,Third Generation Partnership Project (3GPP) Long Term Evolution (LTE)systems, spread spectrum systems (such as Code Division Multiple Access(CDMA) networks), Time Division Multiple Access (TDMA) networks, WiMAX(Worldwide Interoperability for Microwave Access), etc.), provide userswith the convenience of mobility along with a rich set of services andfeatures. This convenience has spawned significant adoption by an evergrowing number of consumers as an accepted mode of communication forbusiness and personal uses. To promote greater adoption, thetelecommunication industry, from manufacturers to service providers, hasagreed at great expense and effort to develop standards forcommunication protocols that underlie the various services and features.One area of effort involves acknowledgment signaling, wherebytransmissions can be implicitly or explicitly acknowledged to conveysuccessful transmission of data. An inefficient acknowledgement schemecan unnecessarily consume network resources.

Therefore, there is a need for an approach for providing efficientsignaling, which can co-exist with already developed standards andprotocols.

SOME EXEMPLARY EMBODIMENTS

According to certain exemplary embodiment, acknowledgement bundling canbe provided for various communication link (e.g., uplink/downlink(UL/DL)) configurations by reusing a Downlink Assignment Index (DAI)field without increasing the length of DAI field.

According to one embodiment, a method comprises dynamically schedulingone or more of subframes per bundling window by reusing an assignmentindex field. The assignment index field has a value greater than orequal to number of previously assigned subframes within the bundlingwindow. The bundling window defines a group of subframes for commonacknowledgement.

According to another embodiment, an apparatus comprises logic configuredto dynamically schedule one or more of subframes per bundling window byreusing an assignment index field. The assignment index field has avalue greater than or equal to number of previously assigned subframeswithin the bundling window. The bundling window defines a group ofsubframes for common acknowledgement.

According to another embodiment, an apparatus comprises means fordynamically scheduling one or more of subframes per bundling window byreusing an assignment index field. The assignment index field has avalue greater than or equal to number of previously assigned subframeswithin the bundling window. The bundling window defines a group ofsubframes for common acknowledgement.

According to another embodiment, a method comprises determining totalnumber of resource grants. The method also comprises determining whetherone or more resource grants have been missed by comparing a value of anassignment index field of a received bundling window with the totalnumber of resource grants. The assignment index field is reused fordynamic scheduling of resources using a bundling window. The bundlingwindow defines a group of subframes for common acknowledgement.

According to another embodiment, an apparatus comprises logic configuredto logic configured to determine total number of resource grants andwhether one or more resource grants have been missed by comparing avalue of an assignment index field of a received bundling window withthe total number of resource grants. The assignment index field isreused for dynamic scheduling of resources using a bundling window. Thebundling window defines a group of subframes for common acknowledgement.

According to yet another embodiment, an apparatus comprises means fordetermining total number of resource grants. The method also comprisesdetermining whether one or more resource grants have been missed bycomparing a value of an assignment index field of a received bundlingwindow with the total number of resource grants. The assignment indexfield is reused for dynamic scheduling of resources using a bundlingwindow. The bundling window defines a group of subframes for commonacknowledgement.

Still other aspects, features, and advantages of the invention arereadily apparent from the following detailed description, simply byillustrating a number of particular embodiments and implementations,including the best mode contemplated for carrying out the invention. Theinvention is also capable of other and different embodiments, and itsseveral details can be modified in various obvious respects, all withoutdeparting from the spirit and scope of the invention. Accordingly, thedrawings and description are to be regarded as illustrative in nature,and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the invention are illustrated by way of example, andnot by way of limitation, in the figures of the accompanying drawings:

FIGS. 1A and 1B are, respectively, a diagram of a communication systemcapable of providing acknowledgement bundling, and a flowchart of theacknowledgement bundling process, according to an exemplary embodiment;

FIGS. 2A-2C are, correspondingly, flowcharts of a process for reusing adownlink assignment index (DAI) field, and a diagram of exemplarydownlink bundle windows, according to various exemplary embodiments;

FIGS. 3A and 3B are, respectively, a flowchart of a process for reusinga downlink assignment index (DAI) field, and a diagram of exemplaryassignments within a bundle window, according to various exemplaryembodiments;

FIGS. 4A-4D are diagrams of communication systems having exemplarylong-term evolution (LTE) and E-UTRA (Evolved Universal TerrestrialRadio Access) architectures, in which the system of FIG. 1 can operateto provide resource allocation, according to various exemplaryembodiments of the invention;

FIG. 5 is a diagram of hardware that can be used to implement anembodiment of the invention; and

FIG. 6 is a diagram of exemplary components of a user terminalconfigured to operate in the systems of FIGS. 4A-4D, according to anembodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT

An apparatus, method, and software for acknowledgement bundling aredisclosed. In the following description, for the purposes ofexplanation, numerous specific details are set forth in order to providea thorough understanding of the embodiments of the invention. It isapparent, however, to one skilled in the art that the embodiments of theinvention may be practiced without these specific details or with anequivalent arrangement. In other instances, well-known structures anddevices are shown in block diagram form in order to avoid unnecessarilyobscuring the embodiments of the invention.

Although the embodiments of the invention are discussed with respect toa wireless network compliant with the Third Generation PartnershipProject (3GPP) Long Term Evolution (LTE) architecture, it is recognizedby one of ordinary skill in the art that the embodiments of theinventions have applicability to any type of communication system andequivalent functional capabilities.

FIGS. 1A and 1B are, respectively, a diagram of a communication systemcapable of providing acknowledgement bundling, and a flowchart of theacknowledgement bundling process, according to an exemplary embodiment.As shown in FIG. 1A, system 100 includes one or more user equipment(UEs) 101 communicating with a base station 103, which is part of anaccess network (not shown) (e.g., 3GPP LTE (or E-UTRAN, etc.). Under the3GPP LTE architecture (as shown in FIGS. 4A-4D), the base station 103 isdenoted as an enhanced Node B (eNB). The system 100, in certainembodiments, utilize an acknowledgement mechanism to provide accurateand timely exchange of information between the UE 101 and the eNB 103.However, such acknowledgement signaling (i.e., using positiveacknowledgements (ACKs) and/or negative acknowledgements (NACKs)) isoverhead, and if not utilized properly can result in degraded networkperformance. To minimize signaling overhead, system 100 employs a schemeto bundle acknowledgement information. In one embodiment, dynamicscheduling of subframes per bundling window is implemented by reusing,for example, a downlink assignment index (DAI) field. Although thebundled acknowledgement scheme is explained with respect to the DAIfield and downlink, it is contemplated that such scheme can be appliedto other equivalent fields and communication link. As used herein,downlink refers to communication in the direction from the eNB 103 tothe UE 101, and uplink refers to communication from the UE 101 to theeNB 103.

The UE 101 can be any type of mobile stations, such as handsets,terminals, stations, units, devices, multimedia tablets, Internet nodes,communicators, Personal Digital Assistants (PDAs) or any type ofinterface to the user (such as “wearable” circuitry, etc.). The UE 101includes a transceiver 105 and an antenna system 107 that couples to thetransceiver 105 to receive or transmit signals from the base station103. The antenna system 107 can include one or more antennas. For thepurposes of illustration, the time division duplex (TDD) mode of 3GPP isdescribed herein; however, it is recognized that other modes can besupported, e.g., frequency division duplex (FDD).

As with the UE 101, the base station 103 employs a transceiver 109,which transmits information to the UE 101. Also, the base station 103can employ one or more antennas 111 for transmitting and receivingelectromagnetic signals. For instance, the Node B 103 may utilize aMultiple Input Multiple Output (MIMO) antenna system 111, whereby theNode B 103 can support multiple antenna transmit and receivecapabilities. This arrangement can support the parallel transmission ofindependent data streams to achieve high data rates between the UE 101and Node B 103. The base station 103, in an exemplary embodiment, usesOFDM (Orthogonal Frequency Divisional Multiplexing) as a downlink (DL)transmission scheme and a single-carrier transmission (e.g., SC-FDMA(Single Carrier-Frequency Division Multiple Access) with cyclic prefixfor the uplink (UL) transmission scheme. SC-FDMA can also be realizedusing a DFT-S-OFDM principle, which is detailed in 3GGP TR 25.814,entitled “Physical Layer Aspects for Evolved UTRA,” v.1.5.0, May 2006(which is incorporated herein by reference in its entirety). SC-FDMA,also referred to as Multi-User-SC-FDMA, allows multiple users totransmit simultaneously on different sub-bands.

In one embodiment, the system of FIG. 1A provides MBMS (MultimediaBroadcast Multicast Services) services in a MBSFN (Multimedia BroadcastSingle Frequency Network). An MBSFN typically has other neighboringMBSFNs or unicast networks operating at the same frequency.

Communications between the UE 101 and the base station 103 (and thus,the network) is governed, in part, by control information exchangedbetween the two entities. Such control information, in an exemplaryembodiment, is transported over a control channel on, for example, thedownlink from the base station 103 to the UE 101.

By way of example, a number of communication channels are defined foruse in the system 100. The channel types include: physical channels,transport channels, and logical channels. Physical channels can includea physical downlink shared channel (PDSCH), a dedicated physicaldownlink dedicated channel (DPDCH), a dedicated physical control channel(DPCCH), etc. Additional, a Physical Uplink Control Channel (PUCCH) isprovided. The transport channels can be defined by how they transferdata over the radio interface and the characteristics of the data. Thetransport channels include a broadcast channel (BCH), paging channel(PCH), a dedicated shared channel (DSCH), etc. Other exemplary transportchannels are an uplink (UL) Random Access Channel (RACH), Common PacketChannel (CPCH), Forward Access Channel (FACH), Downlink Shared Channel(DLSCH), Uplink Shared Channel (USCH), Broadcast Channel (BCH), andPaging Channel (PCH). A dedicated transport channel is the UL/DLDedicated Channel (DCH). Each transport channel is mapped to one or morephysical channels according to its physical characteristics.

Each logical channel can be defined by the type and required Quality ofService (QoS) of information that it carries. The associated logicalchannels include, for example, a broadcast control channel (BCCH), apaging control channel (PCCH), Dedicated Control Channel (DCCH), CommonControl Channel (CCCH), Shared Channel Control Channel (SHCCH),Dedicated Traffic Channel (DTCH), Common Traffic Channel (CTCH), etc.

The BCCH (Broadcast Control Channel) can be mapped onto both BCH andDSCH. As such, this is mapped to the PDSCH; the time-frequency resourcecan be dynamically allocated by using L1/L2 control channel (PDCCH). Inthis case, BCCH (Broadcast Control Channel)-RNTI (Radio NetworkTemporary Identities) is used to identify the resource allocationinformation.

As noted, to ensure accurate delivery of information between the eNB 103and the UE 101, the system 100 utilizes error detection to exchangeinformation, e.g., Hybrid ARQ (HARQ). HARQ is a concatenation of ForwardError Correction (FEC) coding and an Automatic Repeat Request (ARQ)protocol. Automatic Repeat Request (ARQ) is an error detection mechanismused on the link layer. As such, this error detection scheme, as well asother schemes (e.g., CRC (cyclic redundancy check)), can be performed byerror detection modules 113 and 115 within the eNB 103 and UE 101,respectively. The HARQ mechanism permits the receiver (e.g., UE 101) toindicate to the transmitter (e.g., eNB 103) that a packet or sub-packethas been received incorrectly, and thus, requests the transmitter toresend the particular packet(s).

According to one embodiment, downlink hybrid-ARQ acknowledgements in TDDcan be transmitted as a single ACK/NACK feedback where ACK/NACKs fromone or several DL subframes are combined (“bundled” by performing ANDoperation of all A/N) to a single ACK/NACK report and the PhysicalUplink Control Channel (PUCCH) formats already defined for LTE arereused (PUCCH Format 1a/1b). This ACK/NACK mode is referred to as“AN-bundling.” For example, with respect to AN bundling for UL/DLconfigurations (except configuration 5), one implementation is to employa Downlink Assignment Index (DAI) field (e.g. 2-bit), which is added toDCI formats 1, 1A, 1B, and 2. For example, ACK or NACK feedback can beprovided from scheduled DL subframes in which the DAI value of a priorassignment can be compared with a latest assignment to determine anymissed assignments.

In certain embodiments, the downlink assignment index must be greaterthan or equal to the number of previously assigned subframes within thebundling window and must be less or equal to the maximum number ofdynamic assignments within the bundling window. The UE 101 can use theCCE index in last received/detected dynamic DL assignment as well as thesubframe number to (i) check for missed DL assignments and (ii)determine the UL ACK/NACK PUCCH index. Further, it is assumed thatsemi-persistent assignments are not counted in the downlink assignmentindex.

It is recognized that the DAI field is constrained, for example, by2-bits; however, there are up to 9 DL subframes during one bundlingwindow which can be dynamically scheduled. Thus 2-bits cannot fullycover 1-9 DL subframes per bundling window.

To better appreciate the bundling approach of certain embodiments, it isinstructive to describe the following three conventional mechanisms:options 1-3.

In option 1, the two DAI bits indicate if it is the only, first, last,or neither first nor last dynamically assigned DL subframe within thebundling window. The UE can assume that the assigned subframes areconsecutive. The drawback of this option is that it enforces onlyconsecutive time domain scheduling, which is greatly limiting the packetscheduler's flexibility in the packet oriented wireless access system.Thus, performance is degraded, and complexity is increased. Furthermore,this is in contradiction with the scheme agreed for other UL/DLconfigurations.

With option 2, partial sub-frame bundling and ACK/NACK multiplexingscheme is used. The 9 DL sub-frames (including DwPTS) are assigned to X(X>1) bundling windows. For each bundling window, at most 8 ACK/NACKbits can be bundled together regardless of whether it is single codewordor not. ACK/NACK multiplexing scheme is used to transmit multipleACK/NACK bits corresponding to each bundling window. A drawback of thisapproach is that it is not a true AN-bundling scheme, but is amulti-bits scheme—which means that it does not provide an AN-bundlingsolution for 9DL:1UL configuration.

With option 3, an eNB can dynamically schedule at most 4 downlinksubframes to a UE within the bundling window. Remaining downlinkresources (if they exist) can be covered by semi-persistent ormulti-cast assignment. MBSFN subframes can further reduce the unicastdownlink subframes in a bundling window. The drawback is that schedulercannot fully exploit the performance gain from dynamic scheduling forall 9 DL subframes. Also, it is expected that performance degradation isincurred with semi-persistent scheduling due to limited/none frequencyselective gain and low efficiency of resource utilization becauseresources are pre-allocated for each users and can be re-allocated onlyevery rather long time, e.g., a few seconds or even longer.

As shown in FIG. 1B, the approach of system 100 permits a scheduler 117full flexibility to dynamically, as in step 131, schedule any of the,e.g., 9 DL subframes per bundling window by reusing the agreed 2-bitsDAI for other UL/DL configurations (i.e., not increase the length ofDAI). Additionally, from the UE 101 perspective, such mechanism shouldbe simple to adopt. Further, interleaving is employed to decorrelatetime-wise correlations associated with the bundling mechanism (step133). This process, in an exemplary embodiment, is performed by the eNB103 in conjunction with the UE 101 using corresponding acknowledgementbundling logic 119, 121. Further, each of the acknowledgement bundlinglogic 119, 121 can employ an interleaver/deinterleaver 123, 125.

Two approaches are provided: Method 1 and Method 2, as shownrespectively in FIGS. 2A-2C and 3A and 3B. Under Method 1 (detailed inFIGS. 2A-2C), wrap-around the number of scheduler DL subframe into2-bits DAI, and this value is updated every scheduled subframe. WithMethod 2 (detailed in FIGS. 3A and 3B), the process uses (Ceil(Counter/2)+K) modulo 4, where K is a boolean value to indicate whetherat least 2 subframes will be dynamically assigned in the subframeswithin the bundling window. In other words, if there are 0 or 1subframes that will be dynamic assigned in the following subframeswithin the bundling window, K=0; otherwise, K=1. Counter is the numberof scheduler DL subframes and is updated every subframe.

According to certain embodiments, these processes can incorporate aninterleaving method, which introduces a time-wise decorrelation of theconsecutive PDCCHs received. When interleaving, the interleaver map willbreak the regular pattern of the potential correlated PDCCH errors.

FIGS. 2A-2C are, correspondingly, flowcharts of a process for reusing adownlink assignment index (DAI) field, and a diagram of exemplarydownlink bundle windows, according to various exemplary embodiments. Inthis embodiment of Method 1 (as shown in FIG. 2A), a simple extensionfrom the DAI definition can be made for other UL/DL configurations. Instep 201, the process initializes the DAI field. Next, the number ofscheduler downlink (DL) subframe is wrapped around into the DAI field,as in step 203. A counter ‘m’ is utilized to count the number ofscheduled DL subframe; and ‘m’ is updated in each subframe. That is, theDAI field is updated in every scheduled subframe, as in step 205.

Thus, from the eNB side (as seen in FIG. 2B), in step 211, the DAI fieldis set according to m (modulo)×(where m and x are integers); forexample, m MOD 4. From the UE side, the UE 101 will compare, per step213, the value of DAI in the last received DL grant MOD 4 with the totalreceived number of DL grant prior to the last received DL grant (i.e.not including the last receive DL grant) MOD 4 during the bundlingwindow to detect whether some grant(s) have been missed, and AN or DTX(data transmission) will be sent, if the comparison is equal ornon-equal, respectively. If UE 101 has received at least 2 of the same(identical) DAI values during the same bundling window, the value of thelast received DAI should be added ‘4’ (step 215).

FIG. 2C shows an example of DL bundle windows 220, in which bundlewindow #1 specifies DAI values corresponding to subframes 1, 5, and 8.That is, 3 assignments are provided. Bundle window #2 provides DAIvalues corresponding to subframes 2-6, 7, and 9; i.e., 6 assignments.

The above process, according to certain embodiments, provides arelatively simple method for accommodating other UL/DL configuration,and can readily to be added on top the AN bundling for all otherconfigurations (from both standards and implementation point of view).Additionally, there is no restriction imposed on the scheduler 117.

It is noted that a DTX->ACK problem may occur if UE missed 4 consecutiveDL grants, for instance. Although the probability of such case is ratherlow in practice, the eNB 103 can “fall-back” to the conventionaloption-3 (as explained earlier) freely and dynamically to completelyavoid such error case if the eNB 103 foresees that this error may occurand the performance loss is “unacceptable”. That is, this approachprovides for “free & dynamic switch” between Method-1 and Option-3.

FIGS. 3A and 3B are, respectively, a flowchart of a process for reusinga downlink assignment index (DAI) field, and a diagram of exemplaryassignments within a bundle window, according to various exemplaryembodiments. In this embodiment, the eNB 103 labels, as in step 301, DAIfor each assignment as follows: (Ceil (n/2)+K) mod 4, where n is thenumber of previous scheduled assignments within the bundling window, andK (as previously stated) is a boolean value to indicate 0/1 subframe(K=0) or at least 2 subframes (K=1) will be scheduled in followingsubframes within the bundling window.

In step 303, the UE 101 compares two values: sum_DAI_(—)2 last receivedassignments mod 4 and number_of_assignments_before_last_receivedassignment mod 4. If two values are the same (as determined in step305), the UE 101 will send AN (step 307). Otherwise, the UE 101 sendsDTX, per step 309.

FIG. 3B shows an example of the various assignments 320 within a singlebundle. In this example, 9 downlink subframes can provided within onebundle.

The above process, according to certain embodiments, imposes norestriction on the scheduler 117. Also, there is no error case or falseerror probability. It is noted that the eNB 103 has to “pre-estimate”the scheduling decision at least 2 subframe ahead. This, if comparedwith conventional option-3, is less restrictive requirement sincesemi-persistent scheduling for 5 subframes actually mean that eNB 103should do “pre-estimate” the scheduling decision much longer than 2subframe ahead.

As mentioned an interleaving process can be employed with the processesof FIGS. 2A-2C and 3A and 3B. Specifically, an interleaver map providesdecorrelation of time-wise correlations. In one example, a blockinterleaver with 5 columns and 2 rows can be utilized (e.g., forinterleavers 123, 125). When inserting the data into the interleaver125, data is written row-by-row, while the output is readcolumn-by-column. To ensure maximum decorrelation, the first element ofthe interleaver matrix is filled with a “dummy” value, which is ignoredwhen reading from the matrix. The reason for this being that typicallyfor this TDD configuration there are 9 PDCCHs that are to betransmitted. Essentially, using this interleaver map, the sequence:{1,2,3,4,5,6,7,8,9} can be mapped into the sequence {5,1,6,2,7,3,8,4,9},where it is seen that the distance between consecutive PDCCH “counters”will be 4 or 5 depending on the time of observation. It is noted thatintroducing such an interleaver element yields the need to performscheduling decisions 5 subframes ahead (since the DAI signaling value ofsubframe 5 needs to be transmitted in subframe 1 due to theinterleaver). With time-wise decorrelation, the false-positiveprobability will become lower. It is noted that with the use ofinterleaving, there may be a need for a pre-estimation of up to 5subframes, thereby requiring some scheduling ahead (the exact value insubframe 5 needs signaling, so the decisions in subframes 1-4 are alsoneeded).

In certain embodiments, the processes described above can be performedwithin an UMTS terrestrial radio access network (UTRAN) or Evolved UTRAN(E-UTRAN) in 3GPP, as next described.

FIGS. 4A-4D are diagrams of communication systems having exemplarylong-term evolution (LTE) architectures, in which the user equipment(UE) and the base station of FIG. 1A can operate, according to variousexemplary embodiments of the invention. By way of example (shown in FIG.4A), a base station (e.g., destination node) and a user equipment (UE)(e.g., source node) can communicate in system 400 using any accessscheme, such as Time Division Multiple Access (TDMA), Code DivisionMultiple Access (CDMA), Wideband Code Division Multiple Access (WCDMA),Orthogonal Frequency Division Multiple Access (OFDMA) or Single CarrierFrequency Division Multiple Access (FDMA) (SC-FDMA) or a combination ofthereof. In an exemplary embodiment, both uplink and downlink canutilize WCDMA. In another exemplary embodiment, uplink utilizes SC-FDMA,while downlink utilizes OFDMA.

The communication system 400 is compliant with 3GPP LTE, entitled “LongTerm Evolution of the 3GPP Radio Technology” (which is incorporatedherein by reference in its entirety). As shown in FIG. 4A, one or moreuser equipment (UEs) communicate with a network equipment, such as abase station 103, which is part of an access network (e.g., WiMAX(Worldwide Interoperability for Microwave Access), 3GPP LTE (orE-UTRAN), etc.). Under the 3GPP LTE architecture, base station 103 isdenoted as an enhanced Node B (eNB).

MME (Mobile Management Entity)/Serving Gateways 401 are connected to theeNBs 103 in a full or partial mesh configuration using tunneling over apacket transport network (e.g., Internet Protocol (IP) network) 403.Exemplary functions of the MME/Serving GW 401 include distribution ofpaging messages to the eNBs 103, termination of U-plane packets forpaging reasons, and switching of U-plane for support of UE mobility.Since the GWs 401 serve as a gateway to external networks, e.g., theInternet or private networks 403, the GWs 401 include an Access,Authorization and Accounting system (AAA) 405 to securely determine theidentity and privileges of a user and to track each user's activities.Namely, the MME Serving Gateway 401 is the key control-node for the LTEaccess-network and is responsible for idle mode UE tracking and pagingprocedure including retransmissions. Also, the MME 401 is involved inthe bearer activation/deactivation process and is responsible forselecting the SGW (Serving Gateway) for a UE at the initial attach andat time of intra-LTE handover involving Core Network (CN) noderelocation.

A more detailed description of the LTE interface is provided in 3GPP TR25.813, entitled “E-UTRA and E-UTRAN: Radio Interface Protocol Aspects,”which is incorporated herein by reference in its entirety.

In FIG. 4B, a communication system 402 supports GERAN (GSM/EDGE radioaccess) 404, and UTRAN 406 based access networks, E-UTRAN 412 andnon-3GPP (not shown) based access networks, and is more fully describedin TR 23.882, which is incorporated herein by reference in its entirety.A key feature of this system is the separation of the network entitythat performs control-plane functionality (MME 408) from the networkentity that performs bearer-plane functionality (Serving Gateway 410)with a well defined open interface between them S11. Since E-UTRAN 412provides higher bandwidths to enable new services as well as to improveexisting ones, separation of MME 408 from Serving Gateway 410 impliesthat Serving Gateway 410 can be based on a platform optimized forsignaling transactions. This scheme enables selection of morecost-effective platforms for, as well as independent scaling of, each ofthese two elements. Service providers can also select optimizedtopological locations of Serving Gateways 410 within the networkindependent of the locations of MMEs 408 in order to reduce optimizedbandwidth latencies and avoid concentrated points of failure.

As seen in FIG. 4B, the E-UTRAN (e.g., eNB) 412 interfaces with UE 101via LTE-Uu. The E-UTRAN 412 supports LTE air interface and includesfunctions for radio resource control (RRC) functionality correspondingto the control plane MME 408. The E-UTRAN 412 also performs a variety offunctions including radio resource management, admission control,scheduling, enforcement of negotiated uplink (UL) QoS (Quality ofService), cell information broadcast, ciphering/deciphering of user,compression/decompression of downlink and uplink user plane packetheaders and Packet Data Convergence Protocol (PDCP).

The MME 408, as a key control node, is responsible for managing mobilityUE identifies and security parameters and paging procedure includingretransmissions. The MME 408 is involved in the beareractivation/deactivation process and is also responsible for choosingServing Gateway 410 for the UE 101. MME 408 functions include Non AccessStratum (NAS) signaling and related security. MME 408 checks theauthorization of the UE 101 to camp on the service provider's PublicLand Mobile Network (PLMN) and enforces UE 101 roaming restrictions. TheMME 408 also provides the control plane function for mobility betweenLTE and 2G/3G access networks with the S3 interface terminating at theMME 408 from the SGSN (Serving GPRS Support Node) 414.

The SGSN 414 is responsible for the delivery of data packets from and tothe mobile stations within its geographical service area. Its tasksinclude packet routing and transfer, mobility management, logical linkmanagement, and authentication and charging functions. The S6a interfaceenables transfer of subscription and authentication data forauthenticating/authorizing user access to the evolved system (AAAinterface) between MME 408 and HSS (Home Subscriber Server) 416. The S10interface between MMEs 408 provides MME relocation and MME 408 to MME408 information transfer. The Serving Gateway 410 is the node thatterminates the interface towards the E-UTRAN 412 via S1-U.

The S1-U interface provides a per bearer user plane tunneling betweenthe E-UTRAN 412 and Serving Gateway 410. It contains support for pathswitching during handover between eNBs 43. The S4 interface provides theuser plane with related control and mobility support between SGSN 414and the 3GPP Anchor function of Serving Gateway 410.

The S12 is an interface between UTRAN 406 and Serving Gateway 410.Packet Data Network (PDN) Gateway 418 provides connectivity to the UE101 to external packet data networks by being the point of exit andentry of traffic for the UE 101. The PDN Gateway 418 performs policyenforcement, packet filtering for each user, charging support, lawfulinterception and packet screening. Another role of the PDN Gateway 418is to act as the anchor for mobility between 3GPP and non-3GPPtechnologies such as WiMax and 3GPP2 (CDMA 1X and EvDO (Evolution DataOnly)).

The S7 interface provides transfer of QoS policy and charging rules fromPCRF (Policy and Charging Role Function) 420 to Policy and ChargingEnforcement Function (PCEF) in the PDN Gateway 418. The SGi interface isthe interface between the PDN Gateway and the operator's IP servicesincluding packet data network 422. Packet data network 422 may be anoperator external public or private packet data network or an intraoperator packet data network, e.g., for provision of IMS (IP MultimediaSubsystem) services. Rx+ is the interface between the PCRF and thepacket data network 422.

As seen in FIG. 4C, the eNB 43 utilizes an E-UTRA (Evolved UniversalTerrestrial Radio Access) (user plane, e.g., RLC (Radio Link Control)415, MAC (Media Access Control) 417, and PHY (Physical) 419, as well asa control plane (e.g., RRC 421)). The eNB 43 also includes the followingfunctions: Inter Cell RRM (Radio Resource Management) 423, ConnectionMobility Control 425, RB (Radio Bearer) Control 427, Radio AdmissionControl 429, eNB Measurement Configuration and Provision 431, andDynamic Resource Allocation (Scheduler) 433.

The eNB 43 communicates with the aGW 401 (Access Gateway) via an S1interface. The aGW 401 includes a User Plane 401 a and a Control plane401 b. The control plane 401 b provides the following components: SAE(System Architecture Evolution) Bearer Control 435 and MM (MobileManagement) Entity 437. The user plane 401 b includes a PDCP (PacketData Convergence Protocol) 439 and a user plane functions 441. It isnoted that the functionality of the aGW 401 can also be provided by acombination of a serving gateway (SGW) and a packet data network (PDN)GW. The aGW 401 can also interface with a packet network, such as theInternet 443.

In an alternative embodiment, as shown in FIG. 4D, the PDCP (Packet DataConvergence Protocol) functionality can reside in the eNB 43 rather thanthe GW 401. Other than this PDCP capability, the eNB functions of FIG.4C are also provided in this architecture.

In the system of FIG. 4D, a functional split between E-UTRAN and EPC(Evolved Packet Core) is provided. In this example, radio protocolarchitecture of E-UTRAN is provided for the user plane and the controlplane. A more detailed description of the architecture is provided in3GPP TS 86.300.

The eNB 43 interfaces via the S1 to the Serving Gateway 445, whichincludes a Mobility Anchoring function 447. According to thisarchitecture, the MME (Mobility Management Entity) 449 provides SAE(System Architecture Evolution) Bearer Control 451, Idle State MobilityHandling 453, and NAS (Non-Access Stratum) Security 455.

One of ordinary skill in the art would recognize that the processes foracknowledgement bundling may be implemented via software, hardware(e.g., general processor, Digital Signal Processing (DSP) chip, anApplication Specific Integrated Circuit (ASIC), Field Programmable GateArrays (FPGAs), etc.), firmware, or a combination thereof. Suchexemplary hardware for performing the described functions is detailedbelow.

FIG. 5 illustrates exemplary hardware upon which various embodiments ofthe invention can be implemented. A computing system 500 includes a bus501 or other communication mechanism for communicating information and aprocessor 503 coupled to the bus 501 for processing information. Thecomputing system 500 also includes main memory 505, such as a randomaccess memory (RAM) or other dynamic storage device, coupled to the bus501 for storing information and instructions to be executed by theprocessor 503. Main memory 505 can also be used for storing temporaryvariables or other intermediate information during execution ofinstructions by the processor 503. The computing system 500 may furtherinclude a read only memory (ROM) 507 or other static storage devicecoupled to the bus 501 for storing static information and instructionsfor the processor 503. A storage device 509, such as a magnetic disk oroptical disk, is coupled to the bus 501 for persistently storinginformation and instructions.

The computing system 500 may be coupled via the bus 501 to a display511, such as a liquid crystal display, or active matrix display, fordisplaying information to a user. An input device 513, such as akeyboard including alphanumeric and other keys, may be coupled to thebus 501 for communicating information and command selections to theprocessor 503. The input device 513 can include a cursor control, suchas a mouse, a trackball, or cursor direction keys, for communicatingdirection information and command selections to the processor 503 andfor controlling cursor movement on the display 511.

According to various embodiments of the invention, the processesdescribed herein can be provided by the computing system 500 in responseto the processor 503 executing an arrangement of instructions containedin main memory 505. Such instructions can be read into main memory 505from another computer-readable medium, such as the storage device 509.Execution of the arrangement of instructions contained in main memory505 causes the processor 503 to perform the process steps describedherein. One or more processors in a multi-processing arrangement mayalso be employed to execute the instructions contained in main memory505. In alternative embodiments, hard-wired circuitry may be used inplace of or in combination with software instructions to implement theembodiment of the invention. In another example, reconfigurable hardwaresuch as Field Programmable Gate Arrays (FPGAs) can be used, in which thefunctionality and connection topology of its logic gates arecustomizable at run-time, typically by programming memory look uptables. Thus, embodiments of the invention are not limited to anyspecific combination of hardware circuitry and software.

The computing system 500 also includes at least one communicationinterface 515 coupled to bus 501. The communication interface 515provides a two-way data communication coupling to a network link (notshown). The communication interface 515 sends and receives electrical,electromagnetic, or optical signals that carry digital data streamsrepresenting various types of information. Further, the communicationinterface 515 can include peripheral interface devices, such as aUniversal Serial Bus (USB) interface, a PCMCIA (Personal Computer MemoryCard International Association) interface, etc.

The processor 503 may execute the transmitted code while being receivedand/or store the code in the storage device 509, or other non-volatilestorage for later execution. In this manner, the computing system 500may obtain application code in the form of a carrier wave.

The term “computer-readable medium” as used herein refers to any mediumthat participates in providing instructions to the processor 503 forexecution. Such a medium may take many forms, including but not limitedto non-volatile media, volatile media, and transmission media.Non-volatile media include, for example, optical or magnetic disks, suchas the storage device 509. Volatile media include dynamic memory, suchas main memory 505. Transmission media include coaxial cables, copperwire and fiber optics, including the wires that comprise the bus 501.Transmission media can also take the form of acoustic, optical, orelectromagnetic waves, such as those generated during radio frequency(RF) and infrared (IR) data communications. Common forms ofcomputer-readable media include, for example, a floppy disk, a flexibledisk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM,CDRW, DVD, any other optical medium, punch cards, paper tape, opticalmark sheets, any other physical medium with patterns of holes or otheroptically recognizable indicia, a RAM, a PROM, and EPROM, a FLASH-EPROM,any other memory chip or cartridge, a carrier wave, or any other mediumfrom which a computer can read.

Various forms of computer-readable media may be involved in providinginstructions to a processor for execution. For example, the instructionsfor carrying out at least part of the invention may initially be borneon a magnetic disk of a remote computer. In such a scenario, the remotecomputer loads the instructions into main memory and sends theinstructions over a telephone line using a modem. A modem of a localsystem receives the data on the telephone line and uses an infraredtransmitter to convert the data to an infrared signal and transmit theinfrared signal to a portable computing device, such as a personaldigital assistant (PDA) or a laptop. An infrared detector on theportable computing device receives the information and instructionsborne by the infrared signal and places the data on a bus. The busconveys the data to main memory, from which a processor retrieves andexecutes the instructions. The instructions received by main memory canoptionally be stored on storage device either before or after executionby processor.

FIG. 6 is a diagram of exemplary components of a user terminalconfigured to operate in the systems of FIGS. 4A-4D, according to anembodiment of the invention. A user terminal 600 includes an antennasystem 601 (which can utilize multiple antennas) to receive and transmitsignals. The antenna system 601 is coupled to radio circuitry 603, whichincludes multiple transmitters 605 and receivers 607. The radiocircuitry encompasses all of the Radio Frequency (RF) circuitry as wellas base-band processing circuitry. As shown, layer-1 (L1) and layer-2(L2) processing are provided by units 609 and 611, respectively.Optionally, layer-3 functions can be provided (not shown). Module 613executes all Medium Access Control (MAC) layer functions. A timing andcalibration module 615 maintains proper timing by interfacing, forexample, an external timing reference (not shown). Additionally, aprocessor 617 is included. Under this scenario, the user terminal 600communicates with a computing device 619, which can be a personalcomputer, work station, a Personal Digital Assistant (PDA), webappliance, cellular phone, etc.

While the invention has been described in connection with a number ofembodiments and implementations, the invention is not so limited butcovers various obvious modifications and equivalent arrangements, whichfall within the purview of the appended claims. Although features of theinvention are expressed in certain combinations among the claims, it iscontemplated that these features can be arranged in any combination andorder.

What is claimed is:
 1. A method comprising: dynamically scheduling oneor more of subframes per bundling window by reusing an assignment indexfield, wherein the assignment index field has a value greater than orequal to number of previously assigned subframes within the bundlingwindow, the bundling window defining a group of subframes for commonacknowledgement; setting the assignment index field according to mmodulo x, wherein m and x are integers; comparing a value of theassignment index field associated with a last received downlink grantmodulo x with a total number of downlink grants prior to the lastreceived downlink grant modulo x; and adding the value of the assignmentindex field associated with the last received downlink by x, if thereare at least two identical assignment index field values in the bundlingwindow, x being an integer.
 2. The method according to claim 1, furthercomprising: labeling the assignment index field for each assignmentaccording to (Ceil (n/2)+K) modulo x, wherein n and x are integers, andK is a boolean value to indicate whether at least 2 subframes will bedynamic assigned in the subframes within the bundling window.
 3. Themethod according to claim 2, wherein the assignment index field is adownlink assignment index field, and x equals
 4. 4. The method accordingto claim 2, wherein a value of the assignment index field associatedwith a last received downlink grant is compared with a total number ofdownlink grants.
 5. The method according to claim 4, wherein apredetermined number of downlink grants have been missed, and thedynamic scheduling is performed according to a maximum number ofsubframes associated with the bundling window.
 6. An apparatuscomprising: at least one processor; and at least one memory includingcomputer program code, the at least one memory and the computer programcode configured to, with the at least one processor, cause the apparatusto perform at least the following: dynamically schedule one or more ofsubframes per bundling window by reusing an assignment index field,wherein the assignment index field has a value greater than or equal tonumber of previously assigned subframes within the bundling window, thebundling window defining a group of subframes for commonacknowledgement, set the assignment index field according to m modulo x,m and x being integers, compare a value of the assignment index fieldassociated with a last received downlink grant modulo x with a totalnumber of downlink grants prior to the last received downlink grantmodulo x, and add the value of the assignment index field associatedwith the last received downlink by x, if there are at least twoidentical assignment index field values in the bundling window, x beingan integer.
 7. The apparatus according to claim 6, wherein the apparatusis further caused to: label the assignment index field for eachassignment according to (Ceil (n/2)+K) modulo x, wherein n and x areintegers, and K is a boolean value to indicate whether at least 2subframes will be dynamic assigned in the subframes within the bundlingwindow.
 8. The apparatus according to claim 7, wherein the assignmentindex field is a downlink assignment index field, and x equals
 4. 9. Theapparatus according to claim 7, wherein a value of the assignment indexfield associated with a last received downlink grant is compared with atotal number of downlink grants.
 10. The apparatus according to claim 9,wherein a predetermined number of downlink grants have been missed, andthe apparatus is further caused to: dynamically schedule according to amaximum number of subframes associated with the bundling window.